Sanding blocks, which include sanding pads and sanding sponges, of various types are known. Sanding blocks of a first known type are monolithic blocks of pumice or other inherently abrasive materials, which may be porous or nonporous, which may be flexible or inflexible in normal uses, and which may be compressible or incompressible in normal uses. Sanding blocks of a second known type have cores of suitable materials, which may be flexible or inflexible in normal uses and which may be compressible or incompressible in normal uses, with abrasive materials, such as abrasive grit, emery sheets, or sandpaper sheets, which are bonded to the cores. Except as illustrated in the drawings and described herein, particulars of the cores and abrasive materials and of bonding of abrasive materials to the cores are known and are outside the scope of this invention.
As sold by Trim-Tex, Inc. of Lincolnwood, Ill., and admitted here to constitute prior art, a sanding block of the second known type has abrasive grit bonded to a core, which is made of a flexible, compressible, polymeric foam. The sanding block is a six-sided block having two expansive sides, to each of which abrasive grit is bonded, two adjacent sides, to each of which abrasive grit is bonded, and two lateral sides, which do not have abrasive grit and at which the core is exposed. Each adjacent side meets each expansive side at two opposite edges. The sanding block has comparatively coarser, abrasive grit bonded to a given one of the expansive sides and to a given one of the adjacent sides and comparatively finer, abrasive grit bonded to the other one of the expansive sides and to the other one of the adjacent sides.
When viewed macroscopically before the sanding block becomes worn, the sanding block is tapered at its adjacent sides so that a given one of the opposite edges defines an obtuse angle and so that the other one of the opposite edges defines an acute angle in a range from about 55° to about 70°. The acute angle enables a user holding the sanding block in one hand to sand a surface with said expansive side, as far as another surface intersecting the surface being sanded at a right angle, without scuffing the intersecting surface with the adjacent side meeting said expansive side at the acute angle. However, if the user holding the sanding block in one hand applies uneven pressure, gouging of the surface being sanded can occur easily at the opposite edge, which defines the obtuse angle.